India’s ambitious but troubled campaign to inoculate its vast population against Covid-19 — and, in the process, to burnish its reputation as a manufacturer and innovator — received a major lift after initial trial results showed a homegrown vaccine was safe and effective.

Bharat Biotech, the Indian drug company that developed the shots, said late Wednesday that early findings from clinical trials involving nearly 26,000 subjects showed that the vaccine, Covaxin, had an initial efficacy rate of 81 percent.

The results have yet to be peer reviewed, the company said, and it was unclear how effective Covaxin would prove to be in a final analysis.

Still, the results were met with relief in India. Covaxin was approved by government officials in January and administered to millions of people even though it had not yet been publicly proved. Many in the country, including frontline health care workers, had feared that Covaxin could be ineffective or worse, slowing down the national campaign to inoculate 1.3 billion people.

Officials in Brazil, where the government had bought doses of Covaxin, had recently questioned whether the vaccine worked.

The results this week could alleviate some of those concerns, said Dr. Anant Bhan, a health researcher at Melaka Manipal Medical College in southern India. Still, he said, questions will linger over Covaxin until the research is completed.

“This data will now need to be examined by the regulator in India and could then have an impact on the regulatory decisions with regards to the vaccine,” Dr. Bhan said.

If the results hold, they could also benefit Prime Minister Narendra Modi of India, who has stressed his intention of making India self-reliant. An effective, Indian-developed vaccine could add credibility to that campaign.

India approved Covaxin for emergency use in early January along with the Oxford-AstraZeneca vaccine, which is known in India as Covishield. When the vaccination drive started less than two weeks later, most people were not allowed to choose which shot they got.

The move to authorize Covaxin’s use came under sharp criticism from pharmaceutical bodies and health experts, who questioned the scientific logic behind approving a vaccine that was still in trials. Indian officials often denounced those doubts without explaining the rush. Instead, they portrayed the endorsement of Covaxin through a lens of nationalism, saying that it showed India’s emergence as a scientific power.